[akcapr]

i read about your little synth/mishap. I was thinking about making phosphoric acid like u did, just before the actual WP. does anyone know any experiments or synths someone (me) could do using phosporic acid, or would it be more of a new addition to the collection?

[Hephaestus]

Molten Ga + As at room temp does nothing. I thought it might dissolve.
GaAs is formed by heating Ga2O3 in a reducing stream of H2 containing As vapour.
Don't even try this one in lab.
Product is dark gray and brittle. MP 1238C

[Hephaestus]

*GaBr3 is easy to make.
Metallic Ga is heated in a stream of N2 laden with Br2 vapour. A water-clear melt forms first, becoming yellow to re-brown, due to dissolved Br2, when all the Ga hgas reacted. When the bromination is complete, the GaBr3 is distilled in an inert, Br free gas stream into a receiver and hence freed of dissolved Br2.
Properties: Colourlesss, very hygroscopic crystals. MP 121.5C BP 279C
OK Im using a good source for these preps. If I have tried them out, my post will begin with an *.

[YT2095]

I`de like to add a correction to my post #38

it wouldn`t be a RED glow/light I`de be looking for, but a Green one (at 555nm).

take a look here: http://theledlight.com/technical3.html

sorry about that :)

[akcapr]

wat r some stuff do with phosphoric acid?

[budullewraagh]

phosphoric acid is a bit sketchy at times. you can do some unpleasant things with it.

also, you can reduce it to white phosphorus. just please dont ask; phosphorus compounds are generally sketchy.

[akcapr]

sketchy?

[budullewraagh]

yes. consider certain...cholinesterase inhibitors, etc. plus all the oxides and halides of phosphorus arent pleasant. phosphine as well. phosphides arent good either. organophosphates? alkylated phosphorus? scary as hell man.

[YT2095]

can anyone figure this out.

the MP of Gallium is over 30c, the gallium I tried reacting with the red Phos, is still liquid at 19c?

granted the reaction doesn`t seem to have worked for making GaP as there`s still metal there, but it wont solidify unless I put it in the fridge.

what`s going on?

[BenSon]

It's solidifying only very slowly. This happens with my Gallium as well it was liquid at room temperature for a week (if I remeber correctly) before it solidified. Either that or your Gallium is realy pure and has become a super fluid :) which is not likely.

~Scott

[YT2095]

How very odd of it!

I`m pleased it`s something normal though (a refreshing change).
so Gallium has something similar to Hysterisis with it MP transition then, I wonder why?

[jdurg]

Gallium VERY readily becomes supercooled. Apparently the thermodynamics involved with it solidifying does not create a 'greater sense of stability' when it becomes a solid. As a result, it is very happy to stick around as a liquid far below its melting point. This is especially true if your Ga is very pure and there are no contaminations in the container. However once you give it a 'seed' on which to solidify, the solidification happens pretty readily. I guess a good analogy would be a supersaturated solution of something. Until you give it the prodding that it needs to ppt out of solution, it will be quite happy sticking around the way it is.

[collector]

Semiconductor purposes.
It turns out that to get a useful semiconductor is much more than just a chemical synthesis of a semiconductor material like gallium phosphide or arsenide.

Synthesis of gallium phosphide from the elements is one thing.
The production of a working LED is a completely different story!

First, purity. The purity of material for semiconductor purposes need to be at least 99,9999% (=6N). This is because even minute amounts of impurities adversely affects the electrical properties of the material.

Second, crystal form. The material in semiconductors is not just a solid lump of material, it is a pure single crystal of the material. So you must pull a solid crystal of the material from a melt. And of course, the melt as well as the formed crystal has to be protected from even minute traces of contamination.
The vapour pressure of the molten material, as well as the elements, has to be taken into consideration, to prevent some of the materal to evaporise.
In this case the vapour pressure of P; Ga has very low vapour pressure even at elevated temp.

And then there is the problem of doping the stuff.
Then you need some special crystal orientation for the light emission.
Etcetera.

These are some few of the numerous difficult :eek: problems with production of semiconductors.
The subject is more that of solid state physics (semiconductor physics) than inorganic chemistry.

[Hephaestus]

My 50g Ga sample melted in summer (48C) and has stayed liquid since then - down to a chilly 5C on a winters night (how cold is that you northern hemispherians?).
I have sealed it up with parafilm in a HDPE container. Developed an oxide crust after 4 months but still liquid.

[collector]

I have the same experience with gallium. It will stay liquid until disturbed by some small grain of solid matter that induce crystallization. By some reason, the oxide crust does not induce the crystallization process. But a small speck of dust will.


Northern hemisphere: in worst case the temp has fallen down to about -25 degrees centigrade in a really cold winter (south tip of Sweden).
In northern region of Sweden (Lappland), I think the most extreme recorded is about -53 degrees centigrade.
Well below the freezing point of Hg! :eek:

[jdurg]

From experience, I have found that if you take a copper wire and bend it into a tiny little hook and skim the top of the Ga, not only will the oxide adhere to the Cu fairly strongly, but it will initiate crystallization of the liquid Ga. I used this method to clean off the top of my gallium while it was still liquid, and when it solidified shortly thereafter, the surface was bright and reflective while staying completely free of oxide.

[collector]

No risk of contaminating the Ga with copper?
Probably, it won´t be much anyway.

[jdurg]

Very little, if any contamination. The only places where I saw some contamination was at the bottom of the vial where I was really scraping hard to get rid of some oxide that adhered to the glass. Where I was scraping, you can see a very faint blue tint from probably a small bit of copper that went into solution, so to speak.

[H2SO4]

so why does Cu initiate crystal growth? is it from copper contamination?

[jdurg]

It's because the copper wire creates a 'disturbance' in the Ga and provides a spot where crystallization can begin. It's basically a 'seed' for the Ga to grow on.